In the emerging telecommunications environment, optical transport network (OTN) are employed to achieve large capacity of data transmissions at the rates of 1 Giga bits/sec., up to 100 Giga bits/sec., by flexible scheduling of bandwidth without disrupting the continuous data flow, which can be achieved based on optical transmission technologies like Hitless Adjustment of ODUflex (Generic Framing Procedure) (HAO). The HAO as per ITU-T G. 7044 describes the mechanism for bandwidth increase or decrease for an ODUflex (GFP) end to end circuit. The process of increasing or decreasing the bandwidth in a hitless manner involves signalling in two parts consisting of Link Connection Resizing (LCR) and Bandwidth Resizing (BWR), done by signalling protocols viz. LCR protocol and BWR protocol between the Nodes carrying the ODUflex circuit end to end.
A packet client is mapped to an ODUflex via GFP and carried over in an OTN network. Based on client service requirements the ODUflex needs different bandwidth to meet different data flow adjustments. The required increase or decrease in bandwidth is sensed, and a management plane entity (for e.g., network management system) or a control plane entity, (for e.g., Generalised Multi-Protocol Label Switching) commands each of the Nodes in the network to increase or decrease the bandwidth. The command essentially consists of agreed time-slots on each of the nodes where the increased or decreased data flow is to be adjusted. The list of time-slots on which the increase or decrease is to be done is deduced by the management or control plane which has a complete network view.
Since OTN is a circuit switched time-division multiplexed technology, an agreement has to be done between the nodes on the time-slots on which the ODUflex is carried. When a circuit is made, both the transmit and receive ends have to agree on the same list of time-slots which the ODUflex occupies within a higher order ODU (optical channel data unit). In case of bandwidth increase, the LCR protocol involves handshaking between the two nodes on a list of additional time-slots which are proposed for bandwidth increase. The LCR protocol involves coordination between the transmit and receive ends for the resizing operation on these additional time-slots.
The problem with the existing ODUflex bandwidth adjustment technology is that the LCR protocol for ODUflex bandwidth increase or decrease does not identify the time-slots on the connection link between the nodes and these time-slots on which the bandwidth increase or decrease is to be done are decided externally by the management or control plane. Also, in case of network management system (NMS) or control plane signaling (GMPLS) failure the ODUflex resizing is affected. The need for a management plane or control plane entity is necessary for the existing resizing operation as they have the full network view so that they can decide on the matching time-slots at the transmit and receive nodes.
Further the network management system or control plane stack is often associated with a cost. The HAO system has to be integrated with such a stack which requires effort, man power, system resources in terms of CPU/Memory/Power etc. Additionally in control plane signalling a dedicated in-band or out-band communication channel is required thereby resulting in wastage of resources. Therefore a hitless ODUflex resizing method is required which is managed without network management system or control plane signalling including Generalised Multi-Protocol Label Switching (GMPLS).